There is shock among folks in Boston in the wake of the out-of-nowhere trade that sent beloved center Kendrick Perkins and Nate Robinson to Oklahoma City for forward Jeff Green and center Nenad Krstic. Perkins, after all, was seen as the linchpin to the Boston defense for the last three years, a presence who could not only take up space in the middle against weaker teams, but guard the likes of Dwight Howard and Andrew Bynum in crucial playoff matchups. Even among players on the Celtics roster, a source says, there is anger and dismay over the move to send Perkins out of town.

But there’s more to this deal than what’s on the surface for the Celtics. For one thing, Boston general manager Danny Ainge made this trade with one eye on the future. The Celtics have to start thinking about what comes after the Big Three of Ray Allen, Paul Pierce and Kevin Garnett. They seem to be, coincidentally, reconstructing the 2007 draft night trade that brought in Allen and Glen Davis for Green and Delonte West, who was re-signed by the Celtics in the offseason.

Kendrick Perkins (AP Photo)

And it’s difficult to tell where the rest of this deal will lead, because the Celtics also conducted a roster-spot giveaway at the deadline. They sent oft-injured small forward Marquis Daniels to Sacramento for cash, and dealt center Semih Erden and Luke Harangody to Cleveland for a second-round draft pick.

That means the Celtics have three—count them, three—roster spots available. Yeah, the No. 1 seed in the Eastern Conference can sit back, wait for waived veteran players to shake out over the next few days and completely remake a bench that, though talented, has been a scattered mess of injuries and uncertainty. Daniels might not return this season, Jermaine O’Neal had knee surgery, Robinson continues to baffle with bad shot selection, and West is coming off wrist surgery.

The Celtics, according to one agent, “are going to be destination No. 1 for anybody who gets a buyout.” In other words, after injuries ruined the first crack they took at building a complete second unit in the offseason, the Celtics can do it all over again on the fly.

With Rasheed Wallace apparently staying retired, there appears to be one prime option for bench big man: Forward Troy Murphy, when and if the Warriors release him. The Celtics could also pursue perimeter help—Philadelphia’s Jason Kapono, Indiana’s T.J. Ford and Mike Bibby, traded from Atlanta to Washington, could eventually get buyouts, too.

Losing Perkins is difficult, and it’s caused some anger in and around Boston. A poll on Boston.com asking whether the deal was a good one for the Celtics stood at 75 percent "No" with 4,200 votes counted. But the core of the Celtics is signed only through 2012, and at that point, the team is in position to remake itself around point guard Rajon Rondo and Green—with the Clippers’ 2012 draft pick also part of the deal and plenty of cap space available to pursue the likes of, say, Dwight Howard.

And though losing Perkins will hurt the defense—38-year-old Shaquille O’Neal is sure to take over as the starter—consider what the Celtics bench could look like once the dust settles—West, Von Wafer, Green, Glen Davis and Krstic with, perhaps, some combination of Bibby, Kapono, Murphy or Wallace. That’s a wave of players no team in the league can match.

The trade is risky, and it’s too early to size up how the Celtics did. But if things go as Boston hopes, it could be a move that not only pushes the Celtics back to the Finals, but puts them in position to rebuild the roster as they go forward.